1. Field of the Invention
The present invention relates to a process for producing aromatic polyester fibers having high strength and high modulus from aromatic polyesters which are liquid crystals in the melt and the fibers produced by such a process.
2. Discussion of the Background
Aromatic polyester fibers obtained from polymers which form anisotropic melts have a high strength and high modulus and also excellent resistance to heat, chemicals, and the like, and, hence, have attracted much attention. As processes for obtaining such high strength aromatic polyester fibers, Japanese Patent Publication No. 24407/1982 describes a process which comprises heating and stretching an oxybenzoyl copolyester fiber to improve its strength and modulus, and Japanese Patent Publication No. 20008/1980 discloses that heat treatment of an anisotropic melt in an inert atmosphere can increase the strength by 50%.
However, the fibers obtained by the above processes suffer from the drawbacks of readily forming fibrils and being buckled, thereby being inferior in abrasion resistance and resistance to fatigue, since the rigid molecules constituting the fibers are highly oriented. Further, heat treatment for a long-time in an inert atmosphere is required to achieve high strength, which increases the amount of the inert gas used and results in a greater cost.
Thus, there remains a need for a process for producing aromatic polyester fibers which, while maintaining a high strength, are not readily buckled and possess high fatigue resistance and abrasion resistance and the fibers produced by such a process.